While Seddon has embedded a number of Sotkin's photos, which show him in southern Russia taking selfies, it's this one the communications specialist posted, in rebel-controlled Krasna Talycha in east Ukraine, that's most intriguing:

Russia has repeatedly denied having troops inside east Ukraine. So this seemingly harmless selfie may have just blown the whole show. The soldier also posted another photo of himself on July 5, from Krasny Derkul, which is also in Ukraine:

With Instagram's geotagging feature, these two photos pulled the latitude and longitude from the GPS on his phone or tablet, placing him well inside Ukraine. Location data is added to photos as long as the user selects "add to photo map" before posting.

Since it's based on GPS data, geolocation on Instagram is usually pretty accurate. However, as Seddon writes in his post, there is always the possibility Sotkin "spoofed" his GPS signal, or more simply put: used equipment to fake a location signal.

Even if that's the case, it doesn't seem it would make much sense.Instagram/sanya_sotkinThe soldier's photo map.

There's reason to be skeptical; it just seems strange Russian military involvement in the region could be revealed in such a way:

But it's believable if you consider these types of operational security (OPSEC) issues are so common in the U.S. military that troops are required to go through formal training to learn of the dangers. One only needs to search certain military-specific hashtags on Instagram to find all kinds of photos of U.S. military personnel stationed worldwide.

"A U.S. Government official on sensitive travel to Iraq created a security risk for himself and others by tweeting his location and activities every few hours," one briefing slide reads from the U.S. Army's Joint Base Lewis-McChord, which warned of the dangers. In mentioning geotagging, the brief noted the location-based services "bring the enemy right to the Army's doorstep."

Still, U.S. intelligence and a vast amount of open-source data, like social media posts and videos from east Ukraine, have offered a large amount of evidence suggesting that Moscow has been supplying pro-Russian separatists with training, intelligence, and sophisticated weapons systems.

While the pro-Russian separatists in eastern Ukraine are tied to Russian intelligence, there hasn't yet been clear evidence of the Russian military operating across the border. However, there have been reports of Russian troops firing artillery over the border in recent days, according to Washington Post.

It's worth mentioning that Moscow denied having troops in Ukraine's Crimea as well, before Russian President Vladimir Putin finally acknowledged "Crimean self-defense forces were of course backed by Russian servicemen" in April.